Metering valves are known in the art and have been variously utilized in a number of applications, such as public washrooms, urinals, restaurants, etc., wherever it is desired to control and meter a flow of fluid. Typically, these valves are manually actuated and permit a metered quantity of water to be dispensed before automatically shutting off. The valves are typically spring biased to a closed position with the time required for the valve to return to its closed position corresponding to the time (and thus quantity) fluid allowed to flow through the valve. The valves operate with a pressure chamber, or dashpot, wherein fluid on one side of a piston or similar member must be vented or metered to allow the piston to move to its closed position in order to shut off the valve. Various embodiments are known in the art for metering or venting the pressure chamber for this purpose.
Fluid metering is typically accomplished by manipulating fluid pressures within the pressure chamber by means of various valve or fluid passage arrangements that communicate with the main fluid flow controlled by the metering valve. Thus, the fluid flowing through the valve is also used to control the valve's operation. Valve performance may be impaired, however, when a valve fluid, such as water, tends to corrode metal or carries debris which can clog narrow valve passages.
To address these problems, metering valves have been constructed using a dashpot liquid that is isolated from water flow through the valve. The use of selected isolated liquids reduces the occurrence of corrosion and clogging. Such valves, however, must be adequately sealed. Furthermore, they may still be subject to valve "chattering" which can occur when air or other gas trapped in the chamber inhibits valve closure.
The present invention relates to a relatively uncomplicated alternative solution to manipulating pressures within the pressure chamber which reduces the detrimental effects often caused by tapping from the main fluid flow within the valve.